Transit refrigeration control apparatus and method

ABSTRACT

A refrigeration control apparatus for a space includes a heat exchanger mounted in the space and having an inlet and an outlet for a cooling medium to be introduced into and exhausted from the heat exchanger; at least one fan assembly mounted in the space and operatively associated with the heat exchanger for moving an airflow over the heat exchanger; a sensor assembly mounted in the space for sensing a temperature of at least the space; and a controller having an electrical connection to the at least one fan and the sensor assembly to control operation of the fan responsive to the temperature of at least the space. A method is also provided for controlling the temperature of the space.

BACKGROUND

The present embodiments relate to in transit refrigeration (ITR) systems and control systems therefore.

Known control systems for cryogenic in transit refrigeration do not operate at maximum system efficiency. That is, in current cryogenic systems, the heat load from fans for the system provides, in certain cases, the largest system heat load and is therefore responsible for a greater consumption of the cryogen. The fans are operated either in “on” or “off” state, and drive a given maximum flow rate of air through a heat exchanger disposed on board and with the process during the entire in transit chilling or freezing process. In addition, known in transit refrigeration systems rely upon a single temperature probe disposed in the refrigerated compartment and it is the single temperature probe upon which control of the known systems is exclusively relied upon.

BRIEF DESCRIPTION OF THE DRAWING

For a more complete understanding of the present embodiments, reference may be had to the following description taken in conjunction with the drawing Figure, of which:

The Figure shows an embodiment for an in-transit refrigeration control apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figure, it is only necessary to operate the present ITR apparatus fans at maximum speed during initial cool down times when a temperature of the compartment needs to be rapidly brought to a set point temperature. In addition, depending upon the environment in which the in transit system is being operated, the fans can be operated at low speeds and even in some instances completely turned off during extended periods of time during transportation. Moreover, the necessary rate of cool down for the compartment can be optimized so that the fans do not need to be functioning at 100 percent full power and/or capacity for extended periods of time. By using intelligent control logic, a significant power savings can be obtained which contributes to overall cryogen efficiency increases for the present system.

Referring to the Figure, the in-transit system apparatus is shown generally at 10. The apparatus 10 is mounted for operation in a space 12 of a container 14 which is constructed for intermodal transportation. The container 14 therefore can be transported on a truck 16, barge, ship, or other intermodal platform.

The apparatus 10 includes a heat exchanger 18 mounted in the space 12 and provided with a cryogen inlet 20 and a cryogen outlet 22. The cryogen outlet 22 is usually mounted for gaseous cryogen to be exhausted external to the space 12 so as to protect personnel and perhaps cargo 24 being transported in the space. The cargo 24 may consist of food products. A door 26 or doors provide access to the space 12 of the container 14. A sensor 27 or tripswitch is mounted to the door 26 for a purpose described hereinafter.

The apparatus also includes a plurality of temperature sensors 28 or probes (a-h) disposed in the space 12 and for use with the cargo 24. The temperature sensors 28 are indicated also as T1-T8. For example, T1-T2 are disposed in the space 12 to sense the temperature T1 at the heat exchanger 18, while the sensor T2 is disposed near an outlet of the heat exchanger to sense the temperature of an airflow 30 being discharged from the heat exchanger into the space 12.

By sensing and measuring a temperature along the cubic dimensions of the space 12 (length, height and width), it can be determined whether fans 32,34 or blowers are effective in distributing the airflow within the space, or whether a speed of the fans needs to be adjusted or modulated accordingly. Fan 32 may be mounted for operation near an inlet of the heat exchanger 18, while fan 34 may be mounted for operation near an outlet of the heat exchanger. The arrangement of the fans 32,34 facilities airflow across the heat exchanger. For example, if the temperature probes T2-T4 display temperatures less than an acceptable range (such as for example +/− 0.5 F), the speed of the fans 32,34 can be reduced until the temperature range is satisfactory for the space and the cargo 24 contained for being transported therein. A similar approach can be taken with respect to monitoring the temperature gradients at an upper level of the atmosphere in the space 12 as compared to a bottom or lower level of the atmosphere in the space of the container 14. Moreover, if for whatever reason the door 26 to the space 12 is opened, such would trigger or actuate the sensor 27 and thereafter transmit a signal through the wiring 42 or conduit interconnecting the sensor and a controller 36 which will stop operation of the fans 32,34 and accordingly the cryogen flow in the heat exchanger 18 so that cryogen is not wasted during for example a delivery when the door is opened. Similarly, when the door 26 is closed, such action will be communicated by the sensor 27 to the controller 36 to resume operation of the fans 32,34 if necessary.

As shown in the Figure, the sensors T5-T8 can be disposed along a lower level of the atmosphere of the space 12, as discussed above, since there is a temperature gradient between the upper and lower layers of the atmosphere in the space.

When in transit refrigeration and transport of the cargo is to begin, initial cool down of the space 12 will be necessary because the desired set point for the cargo has most likely not been reached. An operator of the truck 16 can therefore have the option of entering a cool down rate for the apparatus 10 to conform to that which is needed for the cargo 24 and accordingly, the fans 32,34 and the cryogen introduced into the cryogen inlet 20 would be operated at a satisfactory rate to provide the necessary cool down. In effect, the ability of the fans 32,34 to unnecessarily consume cryogen due to the heat load they produce can be effectively minimized by limiting use of the fans to only those times when the cool down to reach the set point for the cargo 24 is necessary.

The present embodiments provide for reduced overall power consumption and accordingly, cryogen efficiency is increased commensurately.

The present embodiments of the invention provide control logic used to regulate operation of the fans 32,34 in order to minimize overall heat load on the ITR process. As mentioned above, known ITR systems rely only upon an on/off control and are therefore very ineffective and inefficient with respect to control of the use of the chilling medium such as cryogen used in the space 12. By using the control logic and the array of temperature sensors 28 (T1-T8) at the space 12 of the container 14, data is provided to establish a control scheme for optimum cooling of the refrigerated space 12. By adjusting speed of the fans 32,34, less power is distributed to the refrigerated space 12 in the form of heat and therefore overall efficiency of the ITR process is increased. The controller 36 can communicate with the temperature sensors 28 either by being wired such as shown at 38 for example to each one of the sensors T1-T8, or wirelessly communicating as indicated at 40 with each one of the temperature sensors 28.

It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired result. 

What is claimed is:
 1. A refrigeration control apparatus for a space, comprising: a heat exchanger mounted in the space and having an inlet and an outlet for a cooling medium to be introduced into and exhausted from the heat exchanger; at least one fan assembly mounted in the space and operatively associated with the heat exchanger for moving an airflow over the heat exchanger; a sensor assembly mounted in the space for sensing a temperature of at least the space; and a controller having an electrical connection to the at least one fan and the sensor assembly to control operation of the fan responsive to the temperature of at least the space.
 2. The apparatus of claim 1, wherein the electrical connection is wireless.
 3. The apparatus of claim 1, wherein the cooling medium comprises a cryogen.
 4. The apparatus of claim 1, wherein the at least one fan assembly comprises a first fan near the inlet of the heat exchanger, and a second fan near the outlet of the heat exchanger.
 5. The apparatus of claim 1, wherein the sensor assembly comprises a first sensor mounted near the inlet of the heat exchanger, and a second sensor mounted near the outlet of the heat exchanger.
 6. The apparatus of claim 5, further comprising a container in which the space is contained, the container sized and shaped for products to be disposed in the space; and a third sensor mounted at the products.
 7. The apparatus of claim 6, wherein the container comprises a door for providing access to the space, the door including an electrical connection with the controller to signal open/close status of the door.
 8. A method for controlling a temperature of a space, comprising: circulating an airflow through the space; cooling the airflow with a heat exchanger; sensing a first temperature of the space; controlling movement of the airflow through the heat exchanger in response to the first temperature of the space.
 9. The method of claim 8, further comprising: sensing a second temperature of a product in the space; and adjusting the controlled movement of the airflow in response to the second temperature of the product.
 10. The method of claim 9, further comprising: providing an entrance to the space; sensing an open/close status of the entrance to the space, and further adjusting the controlled movement of the airflow in response to the open/close status of the entrance.
 11. The method of claim 9, wherein the product comprises a food product. 